loesche technology - always a step ahead: loesche mills for cement raw material

Download Loesche Technology - Always a Step Ahead: Loesche Mills for Cement Raw Material

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Cement raw material has been almost exclusively ground in roller mills (vertical air-swept grinding mills) since the second half of the 20th Century. Loesche was and is the pioneer of this technology. Hundreds of Loesche mills have been used in the cement industry across the world to the present day. They operate with two, three, four and six rollers.

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  • 1. 1 Loesche-Mills for cement raw material Loesche_Zement_Rohmaterial_11-09.indd 1 17.09.12 11:31

2. 2 Cement raw material has been almost exclusively ground in roller mills (vertical air-swept grinding mills) since the second half of the 20th century. Loesche was and is the pioneer of this technology. Hundreds of Loesche mills have been used in the cement indus- try across the world to the present day. They operate with two, three, four and six rollers. 1928 The first spring-loaded air-swept grinding mill in the world, constructed by the original company Curt v. Grueber Maschinenbau-Anstalt, Teltow near Berlin, is launched onto the market under the name Loesche Mills and has 2 grinding rollers. It already has all the essential features of modern air-swept vertical grinding mills built today. Even the first Loesche mills had an inte- grated dynamic classifier. Several examples of this are deployed in Klingenberg, Europes first coal dust-fired large-scale power plant in Berlin for coal grinding with a raw coal rate of approx. 12 t/h. 1934 Loesche mills are increasingly also used world- wide for limestone and cement raw material. 1937 400 Loesche mills have already been sold for coal, phosphate and cement raw material. 1939 The largest Loesche mill at this time is an LM 16 with two steel spring-loaded rollers, a grinding track diameter of 1,600 mm and pro- duct throughput of 22 t/h. 1948 The company in Teltow is nationalised; the company is newly established under the name Loesche KG in Dsseldorf (West Germany). 1949 1960 Loesche mills supplied in the sizes LM 16 to LM 20 in modern welded construction with two steel spring-loaded rollers and pro- duct throughputs up to approx. 55 t/h. 1961 1970 Development of 2-roller Loesche mills in the sizes LM 22 to LM 28 with the world novelty of a hydropneumatic spring assembly system for product throughputs up to 140 t/h. Loesche technology always a step ahead Loesche Mill Type LM 46.4, Lengerich, Germany, 2003 Loesche_Zement_Rohmaterial_11-09.indd 2 17.09.12 11:31 3. 3 1971 Introduction of a modular system in mill construction: creation of replacement groups of components such as rollers, rocker arm and hydropneumatic spring for constructing mills with 2, 3 and optionally 4 rollers of the same size. The first LM 30.4 and LM 32.4 4-roller mills are sold and have product throughputs of 178 t/h and 215 t/h. 1973 Sale of LM 36.4 und LM 43.4 mills with product throughputs of 260 t/h and 425 t/h. 1989 Sale of the first LM 50.4 with a throughput of 490 t/h. 1996 Sale of the first LM 63.4 with a throughput of 800 t/h. 2005 Sale of the first 6-roller Loesche mills LM 60.6 with a throughput of 740 t/h 2006 2008 14 Mills Type LM 69.4 and LM 69.6 with product throughputs of up to 1200 t/h are sold. In the 1930s Loesche mills are used to grind cement raw material for the first time. The major breakthrough came at the start of the 1960s when rotary kilns with heat exchangers (dry process) are introduced. The following Loesche technological features make the deployment of these mills so successful in the cement industry: Lowspecificenergyconsumption Lowpressurelossthroughlargecross- sectional flow areas in Loesche mills Minimalsoundemissionssothatnosound insulation measures are required Rapidreactiontofluctuatingrawmaterial qualities Rapidreadjustmenttodifferentproduct qualities Useofthekilnexhaustgasesfordry grinding and as a transport medium for the final product to dust separators Loesche Mill Type LM 45.4 roller mill, Elmadag, Turkey, 1995 Loesche Mill Type LM 63.4, Hereke, Turkey, 2002 Loesche_Zement_Rohmaterial_11-09.indd 3 17.09.12 11:31 4. 4 Quality and reliability right from the start are the glob- ally recognised benefits to be derived from Loesche grinding plants. As early as 1928, when the first Loesche mill came onto the market, the grinding principle of the vertical roller grinding mill, with a driven grinding track and spring-loaded rollers was shown to be particularly energy-efficient and reduced the use of natural resources. These advantages of Loesche mills will become ever more important in the light of increasing plant size and the obligation to make more careful use of primary energy. Moreover, the high product throughputs of Loesche mills (up to 1,300 t/h for cement raw material and already 350 t/h for cement clinker and granulated blast furnace slag) result in considerably reduced investment costs compared to two smaller grinding plants. Loesche is a competent partner for its customers from the initial sale to customer service and from punctual project planning to the handing over of the plant. Our maxim is Every Loesche grinding mill must be a reference mill! Our competence is founded on the following key features: Tailor-madeplantconceptsfromplanningtocom- missioning, based on our own experience com- bined with customer wishes Individual problem solutions through optimised process technology Rational solutions with simultaneous planning of cement clinker/granulated blast furnace slag mills and raw meal mills through the use of exchange- able components for all models of mill, extending to the use of identical gear drives Closecooperationwithsuppliersofrotarykilnsin line with customer wishes Customerservice:plantoptimisationandadvice in the case of further technical developments Long-term delivery capability when supplying spare parts Certification in accordance with EN ISO 9001: 2008. Benefits to customers and customer satisfaction Loesche Mill Type LM 60.4, Ras Al-Khaimah, United Arab Emirates, 2005 Loesche_Zement_Rohmaterial_11-09.indd 4 17.09.12 11:31 5. 5 Shipment for further processingTransport to the port Assembly of the grinding table Mill with classifier under constructionAssembly of the lower part of the mill Grinding table of an LM 69 in the foundry Loesche_Zement_Rohmaterial_11-09.indd 5 17.09.12 11:31 6. 6 Working principle, construction and function of Loesche mills Working principle The material to be ground is crushed between the rotating grinding track and the individually guided grinding rollers. Grinding is carried out primarily through the applica- tion of compressive force. A small amount of shear force supports the displacement of crystalline layers in the raw material. This effect occurs through coni- cal rollers whose axes are inclined at 15 compared to the horizontal grinding track. As already demon- strated through comparative studies in the 1930s, this permits ideal fine grinding and at the same time ensures minimum wear. A higher specific grinding pressure is applied com- pared to coal grinding and a lower specific grinding pressure is applied compared to the fine grinding of clinker and granulated blast furnace slag. Hot gases are added in the dry-grinding process to evaporate material moisture. Use is predominantly made of the exhaust gases from the rotary kilns, the heat exchanger or the cement clinker cooler. If none of these sources are available or the heat content of these exhaust gases is insufficient, Loesches own hot gas generators are deployed. In the classifier above the grinding chamber the ground product is separated from the grit which then falls back onto the grinding track for renewed grinding. Construction The familiar basic principle of the modular system patented in 1970 is applied to Loesche mills with two, three, four and six rollers. The rollers together with their lever systems, hydropneumatic springs and hydraulic control systems make up a functional unit. Large or small modules with a different number of rollers (between two and six) can be deployed in the same mill sizes (grinding table diameter). This makes it possible to customise the product to meet specific customer requirements. The following features characterise Loesche technology: Thesupportandpreciseguidingoftherockerarm roller system with its roller bearings takes place in a pedestal with integrated spring system. Hydropneumaticspringloadingoftherollerrocker arm unit with integrated mechanism to lift the rollers serves as an aid for the mills when starting up with a filled grinding track. The rollers are connected in pairs to a common hydraulic unit (except in the case of 3-roller mills). An almost parallel grinding gap is maintained between the grinding rollers and the grinding plates during the entire service life of the grinding parts. Loesche_Zement_Rohmaterial_11-09.indd 6 17.09.12 11:31 7. 7 Loesche Mill Type LM 69.6, Idhan, United Arab Emirates, 2009 View of the grinding chamber of an LM 69.6 Rollers of an LM 69.6 Mill gearbox Gas spring system Rocker arm in working position Hydraulic cylinder Loesche_Zement_Rohmaterial_11-09.indd 7 17.09.12 11:31 8. 8 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 20 21 22 23 24 25 26 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 21 22 23 24 25 26 27 28 1 1110 2 12 3 1

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